What makes a capacitor changes its response time?

[miskol]

i built a peak detector circuit for an ultrasonic receiver circuit. few days a go the response for the output of the peak detector is fast enough that it really follows the up and down of the receiver.

now suddenly (no hardware or software change) the output of the peak detector's response is slower than before, it takes nearly 3 seconds for the value to settle down.

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Peak detector circuit

it's just a simple peak detector circuit. the 2k resistor is just to cutdown the max output so it does not exceed 5V for ADC input. the cap used is 104.

Please comment, thank you.

 

[FvM]

In your circuit, the discharge time constant is undefined. It depends only on unspecified or parasitic parameters as input resistance of the following buffer, oscilloscope probe etc. Try with a defined discharge resistor.

 

[miskol]

Thank you for the reply.